A new rat model of diffuse brain injury associated with acute subdural hematoma: assessment of varying hematoma volume, insult severity, and the presence of hypoxemia

Incidence, risk factors, and clinical outcomes of acute brain swelling associated with traumatic acute subdural hematoma: a retrospective study utilizing novel diagnostic criteria

Background

Post-traumatic acute brain swelling (ABS) is a major cause of elevated intracranial pressure and thus mortality. The current definition of post-traumatic ABS has certain limitations, and there is limited information available regarding ABS associated with traumatic acute subdural hematoma (ASDH).

Objectives

To investigate the incidence, risk factors, and clinical outcomes of ABS associated with traumatic ASDH.

Design

Retrospective study.

Methods

Data for 161 patients diagnosed with traumatic ASDH were retrospectively collected. Novel computed tomography-based criteria were proposed for diagnosing ABS in patients with ASDH and determining its incidence. Univariate and multivariate logistic regression analyses were performed to explore the risk factors of post-traumatic ABS. The Glasgow Outcome Scale (GOS) score, mortality, and functional prognosis of all patients at discharge and the proportion of intraoperative malignant brain bulge in surgical patients were taken as clinical outcome measures.

Results

A total of 45 (28%) patients experienced post-traumatic ABS, exhibiting significantly lower Glasgow Coma Scale scores on admission (p < 0.001). The incidence of hemispheric and whole-brain swelling was 8.1% and 19.9%, respectively. Risk factors independently associated with post-traumatic ABS were: (1) age [odds ratio (OR) = 0.917, p < 0.001]; (2) platelet to white blood cell ratio (PWR) (OR = 0.887, p = 0.012); and (3) traumatic subarachnoid hemorrhage (SAH) (OR = 4.346, p = 0.005). The ABS cohort had a lower GOS score [2 (1-3) versus 4 (3-5); p < 0.001], higher mortality (46.7% versus 6.9%; p < 0.001), and higher proportion of unfavorable functional prognosis (75.6% versus 34.5%; p < 0.001) upon discharge compared to the no ABS cohort, along with higher proportion of intraoperative malignant brain bulge (43.8% versus 0%; p < 0.001).

Conclusion

The incidence of ABS associated with ASDH is significantly high overall. Patients with ASDH who have young age, low PWR, and traumatic SAH are at an increased risk of developing post-traumatic ABS, and therefore of poor clinical outcomes.

Early Onset of Rapid Lesion Growth in an Acute Subdural Hematoma Model in Rats

OBJECTIVE

Acute subdural hematoma (ASDH) leads to the highest mortality rates of all head injuries with secondary brain damage playing a pivotal role in terms of morbidity and mortality. In patients with ASDH, a delay in surgery leads to disproportional mortality. The benefit of (very) early therapy is therefore, a target of ongoing research. As the process of delayed brain damage in ASDH has not yet been described, this study therefore aimed to examine secondary lesion growth in an experimental rat model of ASDH to define the ideal timing for testing potential neuroprotective therapies.

METHODS

Cerebral blood flow was monitored during ASDH induction with 300 μl of autologous blood. Lesion growth was characterized using Hematoxylin-Eosin- , Cresyl-Violet-, and Fluoro-Jade B-staining for early signs of neuronal degeneration. Histological evaluations were performed between 15 minutes and 24 hours after ASDH.

RESULTS

There was a significant reduction of cerebral blood flow after ASDH. Fluoro-Jade B-positive cells were visible 15 minutes after ASDH in the lesioned hemisphere. Nonlinear growth of lesion volume from 3.7 ± 0.4 mm3 to 17.5 ± 0.6 mm3 was observed at 24 hours in Hematoxylin-Eosin-staining.

CONCLUSIONS

The most damage develops between 15 minutes and 1 hour and again between 2 and 6 hours after ASDH. The time course of lesion growth supports the approach of early surgery for patients. It furthermore constitutes a basis for further ASDH research with more clearly defined time windows for therapy in animal models.

Acute subdural haematoma exacerbates cerebral blood flow disorder and promotes the development of intraoperative brain bulge in patients with severe traumatic brain injury

BACKGROUND

Decompressive craniectomy (DC) is a routine procedure used for the treatment of severe traumatic brain injury (TBI) with concomitant acute subdural haematoma (SDH). However, certain patients are prone to developing malignant brain bulge during DC, which prolongs the operative time and worsens patient outcomes. Previous studies have shown that malignant intraoperative brain bulge (IOBB) may be associated with excessive arterial hyperaemia caused by cerebrovascular system disorders. Through a clinical retrospective analysis and prospective observations, we found that the cerebral blood flow of patients who possessed risk factors manifested high resistance and low flow velocity, which severely affected brain tissue perfusion and resulted in the occurrence of malignant IOBB. In the current literature, rat models of severe brain injury-associated brain bulge have rarely been reported.

METHODS

To gain an in-depth understanding of cerebrovascular changes and the cascade of responses related to brain bulge, we introduced acute SDH into the Marmarou model for the preparation of a rat model of high intracranial pressure (ICP) to simulate the pathological conditions experienced by patients with severe brain injury.

RESULTS

With the introduction of a 400-µL haematoma, significant dynamic changes occurred in ICP, mean arterial pressure, and relative blood perfusion rate of the cerebral cortical vessels. ICP increased to 56.9 ± 2.3 mmHg, mean arterial pressure showed reactive decrease, and the blood flow of cerebral cortical arteries and veins on the non-SDH-affected side decreased to < 10%. These changes could not fully recover even after DC. This resulted in generalised damage to the neurovascular unit and a lag effect to the venous blood reflux, which triggered malignant IOBB formation during DC.

CONCLUSION

An excessive increase in ICP causes cerebrovascular dysfunction and brings about a cascade of damage to brain tissue, which forms the basis for the development of diffuse brain swelling. The subsequent heterogeneous responses of the cerebral arteries and veins during craniotomy may be the main cause of primary IOBB. Clinicians should pay particular attention to the redistribution of CBF to various vessels when performing DC in patients with severe TBI.

RETRACTED: Dexmedetomidine exerts neuroprotective effect via the activation of the PI3K/Akt/mTOR signaling pathway in rats with traumatic brain injury

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Concern was raised about the reliability of the Western blot results in Figures 3A, 5C and 7A which appear to have a similar phenotype as many other publications, as detailed here: https://pubpeer.com/publications/7D9475A7397928053FFE9442F8E943; and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. Several additional suspected image duplication issues were also identified in Figures 3A, 5A, and 7A. The journal requested the corresponding authors comment on these concerns and provide the raw data. The authors were unable to provide a satisfactory explanation or the raw data. The Supervision Committee of the National Natural Science Foundation of China launched an investigation into several papers of Jiangsu Normal University, including this one, and found evidence of "Falsification of pictures or data, fabrication of research process, use of others' signatures without consent, and false information in project final reports", as detailed here: https://www.nsfc.gov.cn/publish/portal0/tab442/info85495.htm. The Academic Committee at Jiangsu Normal University requested retraction of the article. The Editor-in-Chief assessed the case and decided to retract the article.

Attenuation of brain edema and spatial learning deficits by the inhibition of NADPH oxidase activity using apocynin following diffuse traumatic brain injury in rats

Diffuse brain injury (DBI) is a leading cause of mortality and disability among young individuals and adults worldwide. In specific cases, DBI is associated with permanent spatial learning dysfunction and motor deficits due to primary and secondary brain damage. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) is a major complex that produces reactive oxygen species (ROS) during the ischemic period. The complex aggravates brain damage and cell death following ischemia/reperfusion injury; however, its role in DBI remains unclear. The present study aimed to investigate the hypothesis that levels of NOX2 (a catalytic subunit of NOX) protein expression and the activation of NOX are enhanced following DBI induction in rats and are involved in aggravating secondary brain damage. A rat model of DBI was created using a modified weight-drop device. Our results demonstrated that NOX2 protein expression and NOX activity were enhanced in the CA1 subfield of the hippocampus at 48 and 72 h following DBI induction. Treatment with apocynin (50 mg/kg body weight), a specific inhibitor of NOX, injected intraperitoneally 30 min prior to DBI significantly attenuated NOX2 protein expression and NOX activation. Moreover, treatment with apocynin reduced brain edema and improved spatial learning function assessed using the Morris water maze. These results reveal that treatment with apocynin may provide a new neuroprotective therapeutic strategy against DBI by diminishing the upregulation of NOX2 protein and NOX activity.

[Postoperative course after acute traumatic subdural hematoma in the elderly. Does the extent of craniotomy influence outcome?]

AIM

The goal of the study was to analyze the short-term outcome after surgical treatment of acute subdural hematomas in two treatment groups in a patient population >65 years. Whether there are disadvantages from invasive treatment or whether advantages can be achieved with the less invasive treatment has not been previously examined in a prospective study.

METHODS

A prospective, nonrandomized study of 50 patients >65 years with acute traumatic subdural hematoma was performed, comparing the short-term outcome after two different primary surgical procedures: limited craniotomy (group A, n=25) and large decompressive craniectomy (group B, n=25).

RESULTS

There were no differences of hematoma volume, degree of midline structure shift, and time from trauma to operation between the two groups. Initial Glasgow coma scale and short-term outcome after 4 weeks measured by the Glasgow outcome score in both groups showed no significant differences.

CONCLUSION

No significant differences between short-term outcome after limited craniotomy versus large decompressive craniectomy were found for patients >65 years, and the results indicate that decompressive craniectomy can be accepted as a surgical treatment option for acute traumatic subdural hematoma even in elderly patients.

Effects of a small acute subdural hematoma following traumatic brain injury on neuromonitoring, brain swelling and histology in pigs

An acute subdural hematoma (ASDH) induces pathomechanisms which worsen outcome after traumatic brain injury, even after a small hemorrhage. Synergistic effects of a small ASDH on brain damage are poorly understood, and were studied here using neuromonitoring for 10 h in an injury model of controlled cortical impact (CCI) and ASDH. Pigs (n = 32) were assigned to 4 groups: sham, CCI (2.5 m/s), ASDH (2 ml) and CCI + ASDH. Intracranial pressure was significantly increased above sham levels by all injuries with no difference between groups. CCI and ASDH reduced ptiO(2) by a maximum of 36 ± 9 and 26 ± 11%, respectively. The combination caused a 31 ± 11% drop. ASDH alone and in combination with CCI caused a significant elevation in extracellular glutamate, which remained increased longer for CCI + ASDH. The same two groups had significantly higher peak lactate levels compared to sham. Somatosensory evoked potential (SSEP) amplitude was persistently reduced by combined injury. These effects translated into significantly elevated brain water content and histological damage in all injury groups. Thus, combined injury had stronger effects on glutamate and SSEP when compared to CCI and ASDH, but no clear-cut synergistic effects of 2 ml ASDH on trauma were observed. We speculate that this was partially due to the CCI injury severity.

Hyperemia beneath evacuated acute subdural hematoma is frequent and prolonged in patients with an unfavorable outcome: a xe-computed tomographic study

OBJECTIVE

To verify the values and the time course of regional cerebral blood flow (rCBF) in the cortex located beneath an evacuated acute subdural hematoma (SDH) and their relationship with neurological outcome.

METHODS

rCBF levels were measured in multiple regions of interest, by means of a Xe-computed tomographic technique, in the cortex underlying an evacuated SDH and contralaterally in 20 patients with moderate or severe traumatic brain injury and an evacuated acute SDH. Twenty-three patients with moderate or severe traumatic brain injury and an evacuated extradural hematoma or diffuse injury served as the control group. Outcome was evaluated by means of the Glasgow Outcome Scale at 12 months.

RESULTS

Values for the maximum (rCBFmax) and the mean of all rCBF levels in the cortex beneath the evacuated SDH were more frequently consistent with hyperemia. The side-to-side differences in the mean of all rCBF and rCBFmax levels between lesioned and nonlesioned hemispheres were greater in patients with evacuated SDH than in controls (P = 0.0013 and P = 0.0018, respectively). The side-to-side difference in the maximum rCBF value was higher in SDH patients with unfavorable outcomes than in controls at 24 to 96 hours and at 4 to 7 days and higher than in patients with favorable outcomes at 4 to 7 days. The widest side-to-side difference in rCBFmax value was more elevated in patients with an evacuated SDH with unfavorable outcome than in patients with a favorable outcome (P = 0.047), whereas no differences were found in controls. The SDH thickness and the associated midline shift were greater in patients with unfavorable outcomes than in those with favorable outcomes.

CONCLUSION

On average, hyperemic long-lasting rCBF values frequently occur in the cortex located beneath an evacuated SDH and seem to be associated with unfavorable outcome.

Acute subdural hematoma in pigs: role of volume on multiparametric neuromonitoring and histology

Traumatic brain injury (TBI) is often complicated by acute subdural hemorrhage (ASDH) with a high mortality rate. The pathophysiological mechanisms behind such an injury type and the contribution of blood to the extent of an injury remain poorly understood. Therefore, the goals of this study were to establish a porcine ASDH model in order to investigate pathomechanisms of ASDH and to compare effects induced by blood or sheer volume. Thus, we infused 2, 5, and 9 mL of blood (up to 15% of intracranial volume), and we compared a 5-mL blood and paraffin oil volume to separate out effects of extravasated blood on brain tissue. An extended neuromonitoring was applied that lasted up to 12 h after injury and included intracranial pressure (ICP), cerebral perfusion pressure (CPP), tissue oxygen concentration (ptiO(2)), biochemical markers (glutamate, lactate), somatosensory evoked potentials (SEP), brain water content, and histological assessment (Lesion Index [LI]). Volume-dependent changes were detected mainly during the first hours after injury. ICP increased to significant levels (p < 0.05) of 36.89 +/- 1.59, 15.52 +/- 0.48, and 11.25 +/- 0.35 mm Hg after 9, 5, and 2 mL of subdural blood, respectively (sham, 4.85 +/- 0.06 mm Hg). The ptiO(2) dropped drastically after 9 mL of subdural blood without recovery in both hemispheres to below 20% of baseline, but was affected little after 2 and 5 mL in the acute monitoring period (maximal drop to 71% of baseline). Later, 5 mL of blood led to a significant increase of ptiO(2) compared to 2 mL ipsilaterally (p < 0.05). Glutamate and lactate showed a comparable pattern with a long-lasting increase after 9 mL of blood and short-lasting changes after 2 and 5 mL. The two smaller volumes caused an increased brain swelling (2 mL, 80.60 +/- 0.34%; 5 mL, 81.20 +/- 0.66%; p < 0.05 vs. sham), a significant LI (sham, 6.4 +/- 1.4; 2 mL, 30.0 +/- 0.95; 5 mL, 32.1 +/- 1.2; p < 0.05 vs. sham), and a reduced SEP amplitude (5 mL, p < 0.05 vs. baseline) at the end of the experiment. A 9-mL led to herniation during the experiment causing dramatical brain swelling and acute histological damage. Comparison of blood volume with paraffin oil showed no significance, indicating that volume alone determines the acute pathophysiological processes leading to a rapidly developing histological damage. Additional effects due to blood contact with brain tissue (e.g., inflammation) may be detected only at later time points (>12 h).

The effect of haematoma, brain injury, and secondary insult on brain swelling in traumatic acute subdural haemorrhage

OBJECTIVE

The high mortality of acute subdural haematoma (ASDH) is largely explained by its frequent association with primary brain damage consisting of contusion and brain swelling. However, the nature and causes of brain swelling after traumatic brain injury are multifactorial and poorly understood. The purpose of this study was to investigate the pathophysiology of brain swelling associated with ASDH in traumatic brain injury.

METHODS

We examined whether the thickness of the haematoma, parenchymal injury, or presence of a secondary insult had an effect on traumatic brain swelling. The variables that might affect the pathophysiology of ASDH were examined, including: (1) age and mechanism of injury, (2) neurological findings, (3) secondary insult and extracranial injuries, (4) pre-operative computed tomography (CT) scan results, and (5) outcome.

RESULTS

A total of 212 patients were included in this study. On CT scan, 159 patients (75.0%) did not have brain swelling, 29 (13.7%) had hemispheric brain swelling, and 24 (11.3%) had diffuse brain swelling. Brain swelling associated with ASDH is caused by secondary insult in addition to parenchymal injury. In the present study, the outcome of ASDH associated with brain swelling was poor, even when treated with early surgical evacuation; the mortality rate of such patients was over 75%.

CONCLUSIONS

Given our findings, it is possible that the poor outcome of ASDH patients depends not only on the characteristics of the haematoma itself, but also on the presence of additional cerebral parenchymal injury and secondary insult.

Stroke in the immature brain: review of pathophysiology and animal models of pediatric stroke

Pediatric stroke research presents many challenges. Relatively low incidence, need for age stratification, diverse etiologies, delays in diagnosis, lack of an established age-based stroke severity scale and outcome measures are only some of the issues that have prevented the implementation of clinical trials in infants and children with stroke. Experimental animal models of pediatric stroke, therefore, are critical to understanding the pathophysiology and management of ischemic brain damage in the immature brain, and provide the necessary platform for future clinical trials. In this review we discuss the pertinent clinical aspects of pediatric stroke, the pathophysiology of stroke in the developing brain and the animal models established to study basic mechanisms as well as translational issues in pediatric stroke.

Basic science; maturation-dependent response of the immature brain to experimental subdural hematoma

In children less than 2 years of age, the radiographic finding of a subdural hematoma (SDH) in the absence of trauma is highly suggestive of inflicted head injury. Little is understood about the unique pathophysiologic response of the immature brain to a SDH. The goal of the current study was to develop an experimental SDH model to determine whether there is a maturation-dependent response of the immature brain to SDH. Fifteen domestic Yorkshire piglets of three different age groups (five each of 5-days, 1-month, and 4-months old) were selected for study. A volume of blood equal to 10% of the intracranial volume (4.5 cc in the 5-day old, 5.4 cc in the 1-month old, and 9.4 cc in the 4-month old) was injected through a right frontal burr hole. Histologic analysis, including hematoxylin and eosin staining and TUNEL staining, was performed at 7 days survival. A significant difference in percentage of injured hemisphere was noted between the 5-day old group and the 1- and 4-month old animals (p = 0.0382). The number of TUNEL-positive cells/HPF increased significantly with increasing animal age (p = 0.0450). The current study demonstrates a significant maturation-dependent response of the immature brain to SDH, with the youngest animals being quite resistant to a SDH alone. This model will allow further study of additional cerebral insults, such as the addition of apnea or seizures, which may act synergistically along with a SDH to overwhelm the innate neuroprotective capacity of the immature brain to traumatic injury.

Caspase-dependent cell death involved in brain damage after acute subdural hematoma in rats

Traumatic brain injury is associated with acute subdural hematoma (ASDH) that worsens outcome. Although early removal of blood can reduce mortality, patients still die or remain disabled after surgery and additional treatments are needed. The blood mass and extravasated blood induce pathomechanisms such as high intracranial pressure (ICP), ischemia, apoptosis and inflammation which lead to acute as well as delayed cell death. Only little is known about the basis of delayed cell death in this type of injury. Thus, the purpose of the study was to investigate to which extent caspase-dependent intracellular processes are involved in the lesion development after ASDH in rats. A volume of 300microL blood was infused into the subdural space under monitoring of ICP and tissue oxygen concentration. To asses delayed cell death mechanisms, DNA fragmentation was measured 1, 2, 4 and 7 days after ASDH by TUNEL staining, and the effect of the pan-caspase inhibitor zVADfmk on lesion volume was assessed 7 days post-ASDH. A peak of TUNEL-positive cells was found in the injured cortex at day 2 after blood infusion (53.4+/-11.6 cells/mm(2)). zVADfmk (160ng), applied by intracerebroventricular injection before ASDH, reduced lesion volume significantly by more than 50% (vehicle: 23.79+/-7.62mm(3); zVADfmk: 9.06+/-4.08). The data show for the first time that apoptotic processes are evident following ASDH and that caspase-dependent mechanisms play a crucial role in the lesion development caused by the blood effect on brain tissue.

Experimental models of traumatic brain injury: do we really need to build a better mousetrap?

Approximately 4000 human beings experience a traumatic brain injury each day in the United States ranging in severity from mild to fatal. Improvements in initial management, surgical treatment, and neurointensive care have resulted in a better prognosis for traumatic brain injury patients but, to date, there is no available pharmaceutical treatment with proven efficacy, and prevention is the major protective strategy. Many patients are left with disabling changes in cognition, motor function, and personality. Over the past two decades, a number of experimental laboratories have attempted to develop novel and innovative ways to replicate, in animal models, the different aspects of this heterogenous clinical paradigm to better understand and treat patients after traumatic brain injury. Although several clinically-relevant but different experimental models have been developed to reproduce specific characteristics of human traumatic brain injury, its heterogeneity does not allow one single model to reproduce the entire spectrum of events that may occur. The use of these models has resulted in an increased understanding of the pathophysiology of traumatic brain injury, including changes in molecular and cellular pathways and neurobehavioral outcomes. This review provides an up-to-date and critical analysis of the existing models of traumatic brain injury with a view toward guiding and improving future research endeavors.

Acute subdural hematoma associated with diffuse brain injury and hypoxemia in the rat: effect of surgical evacuation of the hematoma

The aim of this study was to assess the effect of rapid or delayed surgical evacuation on the physiological consequence and brain edema formation in a rat model of acute subdural hematoma (SDH) coupled with either diffuse brain injury (DBI) or hypoxemia. The SDH was made by an autologous blood injection, while DBI was induced using the impact acceleration model (mild, 450 g/1 m; severe, 450 g/2 m). Physiological parameters measured included intracranial pressure (ICP), mean arterial blood pressure (MABP), cerebral blood flow (CBF), and brain tissue water content. At 1 h (rapid evacuation) or 4 h (delayed evacuation) after the SDH induction, surgical evacuation following a craniotomy was performed using saline irrigation and forceps. The study consisted of three different series, including 400 microL of SDH alone (Series 1), SDH400 + mild DBI (Series 2), and SDH300 + severe DBI + 20 min hypoxemia (Series 3). The hypoxemia was added in Group 3 to produce a steadily increasing ICP. In Series 1 and 2, all rats were randomized into the three following groups: non-, rapid, and delayed evacuation; Series 3 had two groups: non- and rapid evacuation. In Series 1, the surgical evacuation showed no beneficial effects on the brain edema formation assessed at 5 h post-injury. In Series 2, the rapid, but not delayed, evacuation significantly reduced both the increased ICP level and brain water content. The additional insult of hypoxemia (Series 3) resulted in a progressive ICP elevation, persistently depressed CBF, and severe brain swelling. Under this situation, the rapid evacuation exacerbated brain edema. These results have clinical implications for the management of severe traumatic SDH, especially its operative indication and timing.